Many diagnostic and therapeutic medical procedures require transporting a medical device through the body to a particular location. There are two principal routes through the body: through the body tissue (intraparenchymally) or through the blood vessels (intravascularly).
Several methods and apparatus have been developed for the intraparenchymal placement of medical devices in the body. One such method and apparatus, disclosed in Howard et al., U.S. Pat. No. 5,125,888, incorporated herein by reference, employs a magnet releasably attached to the medical device. The device is moved within the body by the controlled application of a magnetic field to the magnet. The magnetic field guides the magnet, which in turn guides the medical device to which it is attached. Once the medical device is in its desired position the magnet is released from the medical device and recovered, typically by manipulating it out of the body with a magnetic field.
While prior methods and apparatus which employed magnetism to position medical devices have numerous advantages, they also had some draw backs. First, recovery of the magnet could be difficult and time consuming, prolonging the medical procedure. Second, in some instances it can be difficult to generate a magnetic field sufficiently strong to move the medical device through the tissue, and in a desired strength and direction to move the medical device along the desired path.